When I was a kid I saw a girl get hit in the head by one of those swings (which, for some reason back then, were made of metal and on hot sunny days they became as hot as a stove top).
Someone was standing on the seat doing some crazy swingin’ and she walked too close to the swing and it took her out. The person doing the swingin’ flew off the thing but was uninjured. The girl who was hit in the head, however, was bleeding profusely from a large gash on her forehead.
It effected me so much that I never ever got on a swing again.